INTRODUCTION. V 



" Animals move and have special organs of locomotion ; few plants move, though 

 minute forms have thread-like processes or vibratile lashes (cilia) resembling the 

 flagella of monads, and flowers open and shut ; but these motions of the higher plants 

 are purely mechanical, and not performed by special organs controlled by nerves. 

 The mode of reproduction of plants and animals, however, is fundamentally identical, 

 and in this respect the two kingdoms unite more closely than in any other. Plants also, 

 like animals, are formed of cells, the latter in the higher forms combined into tissues. 



" As the lowest plants and animals are scarcely distinguishable, it is probable that 

 plants and animals first appeared contemporaneously ; and while plants are generally 

 said to form the basis of animal life, this is only partially true ; a large number of 

 fungi are dependent on decaying animal matter; and most of the Protozoa live on 

 animal food, as do a large proportion of the higher animals. The two kingdoms sup- 

 plement each other, are mutually dependent, and probably appeared simultaneously 

 in the beginning of things. It should be observed, however, that the animal kingdom 

 overtops the vegetable kingdom, culminating in man." (Packard's Zoology.) 



The Cells and Peotoplasm. 

 The fact that the bodies of the higher as well as of the simpler animals are com- 

 posed of cells was discovered by Schwann in 1839. This discovery is the foundation- 

 stone upon which the modern and still young science of Biology has been built. The 

 cell is the morphological unit of the organic world. With cells the biologist can, itl 

 the imagination, reconstruct the vegetable and animal kingdoms. By studying the 

 forms and behavior of single cells and one-celled animals, such as the motions of the 

 Aniceba, one can better understand the structure and physiology of the highest and most 

 specialized forms, even that of man ; for, as Geddes has remarked, " the functions of the 

 body are the result of the aggregate functions of its cells, and are explained by varia- 

 tions or phases of the activities of them." 



Cells are microscopic portions of protoplasm, either with or without a wall. The 

 protoplasm is the most important, the dynamic part of the cell. What, then is pro- 

 toplasm ? As has already been said, it is the possession of this substance which dis- 

 tinguishes living beings from mineral. Huxley, in his " Science Primer," tells us in 

 simple language what protoplasm is. " If a handful of flour mixed with a little 

 cold water is tied up in a coarse cloth bag, and the bag is then put into a large vessel 

 of water, and well kneaded with the hands, it will become pasty, while the water 

 will become white. If this water is poured away into another vessel, and the knead- 

 ing process continued with some fresh water, the same thing will happen. But if the 

 operation is repeated, the paste will become more and more sticky, while the water will 

 be rendered less and less white, and at last will remain colorless. The sticky substance, 

 which is thus obtained by itself, is called gluten; in commerce it is the substance 

 known as maccaroni. 



" If the water in which the flour has thus been washed is allowed to stand for a few 

 hours, a white sediment will be found at the bottom of the vessel, while the fluid 

 above will be clear, and may be poured off. This white sediment consists of minute 

 grains of starch, each of which, examined with a microscope, will be found to have a 

 concentrically laminated structure. If the fluid from which the starch was deposited 

 is now boiled, it will become turbid, just as white of egg diluted with water does when 

 it is boiled, and eventually a whitish lumpy substance will collect at the bottom of the 

 vessel. This substance is called vegetable albumen. 



